1. Field of the Invention
The present invention relates generally to printing presses and more particularly to a device and method for decelerating or accelerating printed products.
2. Background Information
Web printing presses print a continuous web of material, such as paper. In a folder of the printing press, the continuous web then is cut into signatures in a cutting unit and folded.
One way to slow the velocity of the signature is with a fan wheel. Fan wheels comprise a plurality of fan wheel discs defined by a plurality of outwardly projecting curve-shaped fan blades. Fan wheel pockets formed by adjacent pockets receive signatures exiting the folding device. The curved shape and jagged surface of the fan wheels slow the forward movement of the signatures being deposited in the fan pockets. As the fan rotates, the signature is deposited on a delivery system such as a conveyor belt.
A drawback of this device is that because the signatures enter the fan wheel pockets at such high velocity, they forcefully impact against the blades of the fan wheel causing the signatures to tear or otherwise become damaged. Another drawback of these devices is that the signatures cannot be precisely aimed towards the bottom of the fan wheel pockets. The reason the signatures can not be precisely aimed is that as the signatures come off belts leading to the fan wheel, a number of factors come into play, such as the paper caliper, the number of pages in the signature, the nature of the paper, and even the amount of ink thereon, which will all affect the motion of the signature so that, dependent on the cumulative effect of such factors, the signature may land neatly on the bottom of the fan wheel pocket or may recoil backwards or catch on the edge of a fan wheel blade. Once a signature is irregularly positioned on the fan wheel, the signature will be deposited onto the delivery belt irregularly as well and the product stream thereon is likely to contain laterally displaced, unevenly spaced, or skewed signatures, especially where large speed reductions are required.
One way to slow down signatures is a deceleration drum. The deceleration drum comprises a number of rows of grippers rotating between a transfer supply device and a delivery system. The gripper seizes the leading edge of a signature exiting a transporting device in a folding machine. The gripper is attached to a drum, which decreases the velocity of a signature.
However, a drawback of the deceleration drum is the transfer of the signature from the supply device necessitates positioning the deceleration drum so that the gripper rotates in front of the leading edge of the signature being delivered by the supply device; thus, the velocity of the signature being controlled by the supply device should be greater than the tangential velocity of the gripper on the deceleration drum. When the signature has entered the throat of the gripper, the gripper closes and the velocity of the leading edge of the product abruptly changes to match the velocity of the gripper. The abrupt change can result in distortion or tearing of the signature. A further drawback of the device is that the device requires many complicated parts that are subject to mechanical wear and fatigue.
U.S. Pat. No. 5,975,280 purports to disclose a device for transporting flat products to further processing units. The ""280 patent provides for a track forming a continuous loop, a plurality of gripper elements, and a driving module. The gripper elements are arranged on the track and include a gripper for seizing a flat product from a first device and releasing the flat product to a second device. Each gripper element moves independently from each other gripper element along at least a portion of the track. Each gripper element is selectively engaged by the driving module for movement along the track.
The ""280 patent has the disadvantage that a complex arrangement of multiple mechanical parts is necessary to actualize the transfer of the flat products. The complex arrangement leaves the device subject to mechanical wear and fatigue.
Moreover, the complexity of the device complicates repair and servicing.
U.S. Pat. No. 5,794,929 purports to disclose a variable velocity profile deceleration device. The ""929 patent provides for gripping at high speeds a signature from a cutting cylinder, tape system, or other transporting device. The signatures are positively gripped, decelerated through a smooth velocity profile, and delivered to a further processing device such as a single copy gripper conveyor or a stacker. The deceleration device includes a plurality of rotary grippers mounted to a drum, which rotate about an axis under the control of a drive. A control unit monitors the angular position of the rotary grippers and the rotational speed of the rotating drum and individually controls each gripper, causing the gripper to seize a signature exiting the transporting device.
The ""929 patent has the disadvantage that a complex arrangement of multiple mechanical parts is necessary to actualize the transfer of the flat products. The complex arrangement leaves the device subject to mechanical wear and fatigue. Moreover, the complexity of the device complicates repair and servicing.
U.S. Pat. No. 5,452,886 purports to disclose a device for slowing down signatures being transported in a folding machine. The device provides for a plurality of rotary grippers which positively grip signatures exiting a tape conveyor system. A deceleration drum is also provided for slowing down the drums through a smooth velocity profile. The deceleration drum has a plurality of pivot arms pivotally mounted on a pivot disc rotating about a first axis, the pivot arms being connected to a control disc by a control link.
The ""886 patent has the disadvantage that a complex arrangement of multiple mechanical parts, e.g., the pivot disc, is necessary to actualize the transfer of the flat products. The complexity leaves the device subject to mechanical wear and fatigue. Moreover, the complexity of the device complicates repair and servicing.
U.S. Pat. No. 5,560,599 purports to disclose a device for slowing down signatures being transported in a folding machine. The device provides for a plurality of rotary grippers, defined by a set of oppositely rotating upper and lower rollers, which receive the leading edge of the signature exiting a transporting device. A deceleration drum is also provided for slowing down the drums through a smooth velocity profile. The deceleration drum has a plurality of pivot arms pivotally mounted on a pivot disc rotating about a first axis, the pivot arms being connected to a control disc by a control link.
The ""559 patent has the disadvantage that a complex arrangement of multiple mechanical parts, e.g., the upper and lower rollers and the pivot disc, is necessary to transfer the flat products. The complexity leaves the device subject to mechanical wear and fatigue. Moreover, the complexity of the device complicates repair and servicing.
An object of the present invention is to provide for a device and method for continuously handling a signature as it exits a folding device in a printing press and is transported to a delivery system for further processing. An additional or alternative object of the present invention is to provide a device for decelerating consecutive signatures. Yet another additional or alternative object of the present invention is to provide a device for delivering consecutive signatures from a folding device to a delivery system in an orderly fashion with minimal distortion by using a simple elastic belt mechanism.
The present invention provides a device for transporting flat products to further processing units comprising:
a first drive unit;
a second drive unit;
an elastic belt forming a continuous loop, contacting both the first drive unit and second drive unit and moving around the first and second drive units; and
a plurality of grippers arranged on the elastic belt for seizing a flat product from a first device and releasing the flat product to a second device.
With the elastic belt of the present invention, positive signature deceleration is possible with a simpler mechanism, at a lower cost, and with higher reliability.
Preferably, the first and second drive units further comprise a plurality of notches disposed along the rim of pulleys of the first and second drive units and the elastic belt may comprise a plurality of timing lobes disposed on the inner surface of the belt, the timing lobes shaped so as to fit in the notches. The advantage thus provided is the notches work with the timing lobes to provide synchronous rotation between the first and second drive units. Also, accumulative drift of the elastic belt is prevented.
The first and second drive units preferably include pulleys or rolls over which the elastic belt travels.
Preferably, the first drive unit further includes a pulley with a radius different from a pulley of the second drive unit. Advantageously, the different radii produce surface speed differences that alter the speed of the elastic belt and thus the flat product, which is held in the gripper that is attached to the elastic belt. For example, a signature can be picked up at the large radius drive unit at a high speed and dropped off at the small radius drive unit at low speed. The change in radii affects the surface speed of the drive units, which in turn affects the speed of the elastic belt. The speed change of the elastic belt occurs at two speed transition regions, located around the points where the elastic belt contacts the drive units. The folded product transfers may occur at any point, however, it is preferably that the folded products are not transferred in the speed transition regions. The elastic belt stretches and contracts in response to the speed changes.
The first drive unit may further comprise a pulley having a radius the same as a pulley of the second drive unit and the first drive unit may run at a rotational velocity different from the second drive unit. Advantageously, the different rotational velocities produce surface speed differences that alter the speed of the grippers holding the printed or sheet product, which is held in the gripper that is attached to the belt. For example, a signature can be picked up at the fast rotational velocity drive unit at a high speed and dropped off at the slow rotational velocity drive unit at a slow speed. The change in rotational velocity affects the speed of the signature because the slow rotational velocity drive unit operates at a slower surface speed than the fast rotational velocity drive unit, which in turn affects the speed of the elastic belt.
Preferably, the present invention may further comprise at least one power transmission device for driving and synchronizing the first and second drive units. Power transmission devices for each drive unit may be provided, or a single power transmission device with gearing for both drive units may be provided.
Preferably, each of the power transmission devices has an individual motors. Advantageously, repair of a failed element is simple; the motor can be replaced instead of a part of a complex mechanical mechanism. Also, the first and second drive units can be synchronized by setting the speeds of the motors.
The transport device may further comprise a plurality of translatable idler drive units positioned so at to contact the elastic belt and a register mechanism for synchronizing the two power transmission devices, so that phasing between the drive units and the folded material transfer times can occur.
Each of the plurality of translatable idler drive units may further include a plurality of notches disposed along the rim of each translatable idler drive unit.
Preferably, each of the plurality of translatable idler drive units may further include pulleys or rolls. The improved versatility allows the invention to be used in a variety of different configurations in printing presses.
Each of the plurality of translatable idler drive units may have different radii. The differing radii allow the translatable idler drive units to remain in synchronization with the elastic belt.
Preferably, the present invention may further comprise a control system for actuating translation of each of the translatable idler drive units and the register mechanisms. Advantageously, phasing is improved between the drive units and the folded material transfer times.
The present invention also provides a method for changing the speed of a signature including the steps of:
gripping a flat product from a first device with a gripper device attached to a continuous elastic belt;
rotating the continuous elastic belt by a first drive unit and a second drive unit, so as to move the flat product; and
releasing the flat product.
Although the pitch of the belt lobes are uniform if the elastic belt is unstretched, when the elastic belt is in operation, the elastic belt is non-uniformly stretched and non-uniform pitch of the lobes results. Hence, the pitch of the lobes on the first drive unit differs from the pitch on the second drive unit.
The present invention also may provide an elastic belt on pulleys without timing notches. A steady state extension of the belt will occur even though there is a large speed difference between the pulleys. As the belt is driven by one of the drive units, the belt attains the velocity of the drive unit. In so doing, the segment of the belt attaining the velocity of the drive unit will have the same unstretched length when it attains the velocity of the other drive unit. Thus, at the higher velocity the elastic belt has a higher strain and at a lower velocity the elastic belt has a lower strain. The belt velocity transition occurs as the belt leaves the first or second drive units and enters a free span of the belt between the drive units. The timing elements ensure the belt remains synchronized with the first and second drive units so there is no accumulative drift and the first and second drive units are synchronized by the power transfer devices.